Version 5.0 The LEDA User Manual

• indegree stores for every node that corresponds to any iterator the number of incoming
edges (has to be to computed before)
• Queuetype is a queue parameterized with elements of type OutAdjIt
The underlying graph need not be acyclic. Whether or not it is acyclic can be tested after
execution of the algorithm (function cycle found()).
3. Operations
void algorithm.next( ) Performs one iteration of the core loop of the algorithm.
More specifically, the first element of
get queue() is removed from the queue, and every
immediate successor n of this node for which currently
holds get(indeg,n)==0 is inserted in get queue().
void algorithm.finish algo( )
executes the algorithm until finished( ) is true, i.e.
exactly if the queue is empty.
bool algorithm.finished( ) returns true if the internal queue is empty.
OutAdjIt algorithm.current( ) returns the current adjacency iterator.
Queuetype& algorithm.get queue( )
bool algorithm.cycle found( )
void algorithm.reset acyclic( )
4. Implementation
gives direct access to internal queue.
returns true if a cycle was found.
resets the internal flag that a cycle was found.
The asymptotic complexity is O(m + n), where m is the number of edges and n the
number of nodes.
5. Example
This algorithm performs a normal topological sort if the queue is initialized by the set of
all nodes with indegree zero:
Definition of algorithm, where indeg is a data accessor that provides full data access to
the number of incoming edges for each node:
GIT_TOPOSORT algorithm(indeg);